Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$110.67	3.841%	$114.9208	$114.92	$114.90	$114.90
Purchase #2	$207.66	5.733%	$219.5651	$219.57	$219.55	$219.60
Purchase #3	$243.55	8.765%	$264.8972	$264.90	$264.90	$264.90
Purchase #4	$160.71	3.850%	$166.8973	$166.90	$166.90	$166.90
Purchase #5	$165.74	12.777%	$186.9166	$186.92	$186.90	$186.90
Purchase #6	$97.78	13.712%	$111.1876	$111.19	$111.20	$111.20
Purchase #7	$97.93	13.163%	$110.8205	$110.82	$110.80	$110.80
7 purchase totals =	$1,084.04		$1,175.2051	$1,175.22	$1,175.15	$1,175.20